Display devices are generally required to have as wide a viewing angle as possible so that a clear image can be seen from any angle. Various technological developments have been carried out in connection with widening of the viewing angle of liquid crystal display devices. This is particularly because liquid crystal display devices, which have been in widespread use in recent years, include liquid crystal having viewing angle dependence.
However, a narrow viewing angle may be preferable, in a specific use environment. This allows a display content to be visible only to the user. Furthermore, laptop personal computers, personal data assistants (PDAs), portable phones and the like are particularly likely to be used in sites, where the general public may be present, such as in trains and airplanes. In such a use environment, the display device has preferably a narrow viewing angle because it is undesirable to let other people nearby see a display content, in light of reason such as confidentiality protection or privacy protection. As described above, there have been increasing demands in recent years for the ability to switch a viewing angle of a single display device between a wide viewing angle and a narrow viewing angle, in conformity with a use condition. Note that the demands are shared by any display devices, not limited to liquid crystal display devices.
In order to address such demands, Patent Document 1, for example, suggests an arrangement in which a retardation controlling device and a display device for displaying an image are provided and a viewing angle characteristic is changed by controlling a voltage applied to the retardation controlling device. According to Patent Document 1, the liquid crystal used in the retardation controlling liquid crystal display device is exemplified by a chiral nematic liquid crystal, a homogeneous liquid crystal, a randomly aligned nematic liquid crystal, and the like.
Further, Patent Documents 2 and 3, for example, disclose arrangements in which a viewing angle controlling liquid crystal panel is provided above a liquid crystal display panel, these panels are sandwiched by two polarizing plates, and a voltage applied to the viewing angle controlling liquid crystal panel is adjusted so that a viewing angle is controlled. According to Patent Document 2, the liquid crystal of the viewing angle controlling liquid crystal panel is a twisted nematic liquid crystal.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 174489/1999 (Tokukaihei 11-174489; published on Jul. 2, 1999)    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 268251/1998 (Tokukaihei 10-268251; published on Oct. 9, 1998)    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 309020/2005 (Tokukai 2005-309020; published on Nov. 4, 2005)
According to the Patent Document 1, the provision of the retardation controlling liquid crystal device allows switching between a wide viewing angle mode and a narrow viewing angle mode. However, this does not give rise to sufficient effect. For example, Patent Document 1 shows an equal-contrast curve for a contrast ratio of about 10:1, as shown in FIG. 17. This shows that the contrast in a wide viewing angle direction is surely decreased in the narrow viewing angle mode. However, a decrease in contrast to such a degree causes a display to be sufficiently visible to a person next to the user. This is because a display is in general sufficiently visible even if the contrast ratio is decreased, for example, to 2:1.
According to the arts disclosed in Patent Documents 2 and 3, switching between a wide viewing angle and a narrow viewing angle is carried out by changing the voltage applied to the viewing angle controlling liquid crystal panel so that the contrast is adjusted. However, this does not give rise to sufficient effect, either.
Namely, all of the arts disclosed in Patent Documents 1, 2, and 3 adopt a method in which the switching between a wide viewing angle mode and a narrow viewing angle mode is carried out by decreasing the contrast in the wide viewing angle direction. However, according to such a method, blocking off of a view in the narrow viewing angle mode is not sufficient in the wide viewing angle direction, i.e., in a direction in which the narrow viewing angle is not realized. This is likely to cause a problem that a display may be seen by other people.
The present technology addresses the problem discussed above, and aims to provide a display system which is capable of enhancing a blocking effect.
As a result of great devotion to various examinations of the above problem, the inventors have proved that a blocking effect is more enhanced when a display device is used in an environment in which the display device is exposed to external light, and arrived at the present invention.
In order to solve the above problem, a display system of the present technology includes a display device, the display device including: a backlight; a display panel; and a viewing angle control panel for controlling a viewing angle of the display panel, the display system further including a reflected light amount relative increasing section for causing an amount of external light reflected in the display device to be relatively larger than an amount of light leaked from the backlight in the display device. The reason for using the word “relatively” in the above description is that it is also possible to make the amount of reflected light be larger than the amount of light leaked from the backlight, by reducing the luminance of the backlight.
According to the above, the reflected light amount relative increasing section causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight in the display device. This reduces visibility of a display content on the display panel of the display device. As a result, it is possible to provide a display system which is capable of enhancing a blocking effect.
The display device of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes a lighting section for turning on a light for increasing the amount of light reflected in the display device.
Since the lighting section thus turn on a light, it is possible to ensure that the amount of external light reflected in the display device is relatively larger than the amount of light leaked from the backlight.
The display system of the present technology may preferably be such that the lighting section includes the light provided on at least one of four sides surrounding the display device.
This allows a light to be provided on at least one of the four sides surrounding the display device and thereby causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight.
The display system of the present technology may preferably be such that the lighting section includes the light provided so as to face a viewer using the display device.
This allows a light to be provided so as to face a viewer and thereby reduces visibility of a display of the display device, for example, to a person present behind the viewer using the display device, due to an increase in external light reflected in the display device caused by the light.
The display system of the present technology may preferably be such that the display device further includes a touch panel which is provided on a front surface of the display panel and which allows signal input to be entered when part of the touch panel is touched, and the lighting section turns on the light when the tough panel is touched.
This allows a light to be turned on when the touch panel is touched, for example, in a case of operating the display device including the touch panel, which display device is provided in an automatic teller machine (ATM) of a bank. This thereby allows an operator of the display device to prevent a display content from being seen by other people.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes a human sensor for sensing presence of a person, and that the lighting section turns on the light when the human sensor senses presence of a person.
This allows a light to be turned on when the sensor senses the presence of a person. This thereby causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, when an operator using the display device is present. In consequence, when a person is present behind the operator using the display device, the above suppresses visibility of a display to the person present behind the operator.
The display system of the present technology may preferably be arranged such that the display device is provided in a cash dispenser, and that the lighting section turns on the light when a cash card is inserted in the cash dispenser.
The insertion of a cash card into the cash dispenser indicates the presence of an operator using the display device. Turning on a light when a cash card is inserted enhances a blocking effect and prevents a display content to be seen by other people.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes a backlight luminance reducing section for reducing luminance of the backlight.
The luminance of the backlight may be reduced as a method of causing the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight in the display device. This reduces visibility of a display on the display panel of the display device and thereby provides a display system having an enhanced blocking effect.
The display system of the present technology may preferably be arranged such that the display device includes a touch panel which is provided on a front surface of the display panel, and which allows signal input to be entered when part of the touch panel is touched, and the backlight luminance reducing section reduces the luminance of the backlight when the touch panel is touched.
This allows reduction in the luminance of the backlight when the touch panel is touched. Therefore, in a case of operating the display device including the touch panel, which display device is incorporated in an ATM of a bank, touching the touch panel causes the luminance of the backlight to be reduced. This thereby allows an operator of the display device to prevent a display content from being seen by other people.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes a human sensor for sensing presence of a person, and that the backlight luminance reducing section reduces the luminance of the backlight when the human sensor senses presence of a person.
This allows reduction in the luminance of the backlight when the sensor senses the presence of a person. This thereby causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, when an operator using the display device is present. In consequence, when a person is present behind the operator using the display device, the above suppresses visibility of a display to the person present behind the operator.
The display system of the present technology may preferably be arranged such that the display device is provided in a cash dispenser, and that the backlight luminance reducing section reduces the luminance of the backlight when a cash card is inserted in the cash dispenser.
The insertion of a cash card into the cash dispenser indicates the presence of an operator using the display device. Reducing the luminance of the backlight when a cash card is inserted enhances a blocking effect and prevents a display content to be seen by other people.
The display system of the present technology may preferably be arranged such that the human sensor senses the presence of a person with use of infra-red radiation.
This allows the sensor to sense the presence of a person by means of general infra-red radiation and thereby facilitates fabrication of such a sensor.
The display system of the present technology may preferably be arranged such that the human sensor senses presence of a person operating the display device.
This causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, when an operator using the display device is present.
The display system of the present technology may preferably be arranged such that the human sensor senses presence of a person present behind a person operating the display device.
This causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, when a person is present behind an operator using the display device.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes an ambient illuminance sensor for sensing ambient illuminance of the display device, and that the lighting section turns on the light when illuminance sensed by the ambient illuminance sensor is not more than a set value.
This allows the lighting section to turn on a light when it becomes dark in the ambient environment and therefore the luminance sensed by the ambient illuminance sensor is not more than a set value.
This causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight by turning on the light, when, for example, it becomes dark in the ambient environment early in the evening and therefore visibility of the display device becomes better.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section further includes an ambient illuminance sensor for sensing ambient illuminance of the display device, and the backlight luminance reducing section reduces the luminance of the backlight when illuminance sensed by the ambient illuminance sensor is not more than a set value.
This allows the backlight luminance reducing section to reduce the luminance of the backlight when the luminance sensed by the ambient illuminance sensor is not more than a set value.
This causes the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, when, for example, it becomes dark in the ambient environment early in the evening and therefore visibility of the display device becomes better.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section includes a polarizing plate, provided on a front surface of the display device, which has been subjected to a diffusion treatment.
This allows a polarizing plate having been subjected to a diffusion treatment to be provided on the front surface of the display device, and thereby enhances a blocking effect of the viewing angle control panel, as compared to the case in which a polarizing plate not having been subjected to a diffusion treatment is included.
The display system of the present technology may preferably be arranged such that the reflected light amount relative increasing section further includes, in at least a part of an area surrounding the display device, a reflective member for increasing the amount of light reflected in the display device.
This allows a reflective member to be provided in at least a part of the area surrounding the display device, and thereby increases the amount of light reflected in the display device.
This enhances the effect of causing the amount of external light reflected in the display device to be relatively larger than the amount of light leaked from the backlight, which effect is due to the lighting or reduction in the luminance of the backlight.
The display system of the present technology may preferably be arranged such that the reflective member is provided so as to face a viewer using the display device.
This causes external light to be reflected by the reflective member provided so as to face the viewer using the display device, and thereby suppresses visibility of a display of the display device, for example, to a person present behind the viewer using the display device, due to reflected light caused by the reflective member.
The display system of the present technology may preferably be arranged such that the reflective member is a reflective plate which faces, at a variable angle, the display device.
Consequently, changing the angle of the reflective plate which faces, at a variable angle, the display device prevents a display of the display device from being visible from a specific angle.
The display system of the present technology may preferably be arranged such that the viewing angle control panel includes: a liquid crystal cell including: a pair of transparent substrates; and a liquid crystal layer provided between the transparent substrates, the liquid crystal layer having liquid crystal molecules aligned vertically, and a driving circuit for applying a voltage to the liquid crystal layer, that the liquid crystal cell being provided between two polarizing plates which are provided to face each other so that polarizing transmission axes thereof are substantially at right angle, and that the driving circuit changes an alignment of the liquid crystal molecules included in the liquid crystal layer of the liquid crystal cell so that a display state is switched between a first viewing angle range and a second viewing angle range which is within the first viewing angle range and is narrower than the first viewing angle range.
According to the above, the two polarizing plates having polarizing transmission axes which are substantially at right angle are provided so as to sandwich the liquid crystal cell of the viewing angle control panel. The viewing angle control panel and the two polarizing plates are not necessarily adjacent to each other. There may be another element therebetween.
According to the above arrangement, application of a predetermined voltage to the liquid crystal layer causes the alignment of the liquid crystal molecules to change. Use of birefringence of the liquid crystal allows a change in the polarization of light to be emitted from the liquid crystal cell of the viewing angle control panel. The polarizing plate provided on the side of the viewing angle control panel which side faces a viewer serves as an analyzer. Consequently, the light to be emitted from the viewing angle control panel toward the viewer is either transmitted or blocked depending on the angle. In other words, the display state is capable of being switched between (i) a wide viewing angle which forms the first viewing angle range and (ii) a narrow viewing angle which forms the second viewing angle range, which is within the first viewing angle range and narrower than the first viewing angle range. It should be noted that the terms “wide viewing angle” and “narrow viewing angle” do not refer to any specific, absolute angle ranges. They refer to a relatively wide viewing angle and a relatively narrow viewing angle.
According to the above arrangement, the use of the liquid crystal cell having liquid crystal molecules aligned vertically allows a narrow viewing angle mode to be achieved in which mode a display is only visible from within a limited viewing angle. This allows a viewing angle control by switching between transmission and blocking of light, unlike the conventional art of controlling a viewing angle in which art the contrast of a display is decreased in the wide viewing angle direction. This causes the amount of external light reflected in the display device to be larger than the amount of light leaked from the backlight, even in the narrow viewing angle mode, and thereby enhances a blocking effect.
The display system of the present technology may preferably be arranged such that the display panel is a liquid crystal display panel. The liquid crystal display panel may be a transmissive liquid crystal display panel, a reflective liquid crystal display panel, or a semi-transmissive liquid crystal display panel.
This provides a display system including a liquid crystal display panel and having an enhanced blocking effect.
For a fuller understanding of the nature and advantages of the example embodiments presented herein, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.